<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
  <style>
    #d1{
      width: 100px;
      height: 100px;
      border: 1px solid red;
      /*单独某一个方向添加外边距*/
      margin-left: 100px;
      margin-top: 100px;
      /*四个方向添加外边距*/
      margin: 50px;
      /*上下和左右赋值*/
      margin: 50px 100px;
      /*外边距实现居中
        左右auto代表自动，左右自动为居中*/
      margin: 0 auto;
      /*上右下左顺时针赋值*/
      margin: 10px 20px 30px 40px;
    }
    #d2{
      width: 100px;
      height: 100px;
      border: 1px solid red;
      /*上下相邻 彼此添加外边距 取最大值*/
      margin-top: 50px;
    }
    span{
      border: 1px solid blue;
    }

    #s1{
      margin-right: 50px;
      /*行内元素上下外边距无效*/
      margin-bottom: 50px;
    }
    #s2{
      /*左右相邻彼此添加外边距，两者相加*/
      margin-left: 50px;
    }
    #big{
      width: 200px;
      height: 200px;
      background-color: red;
      overflow: hidden;
    }
    #big>div{
      width: 50px;
      height: 50px;
      background-color: green;
      margin-left: 100px;
      /*当元素的上边缘和上级元素的上边缘重叠时，
      给元素添加上外边距会出现粘连显示异常，
      给上级元素添加overflow：hidden解决*/
      margin-top: 100px;
    }
  </style>
</head>
<body>
<div id="big">
  <div></div>
</div>
<span id="s1">span1</span>
<span id="s2">span2</span>
<div id="d1"></div>
<div id="d2"></div>
</body>
</html>